[ATF] add checks filter in policy Allow studio to control which sets of validations to run. Also added few more tests. Bug: 150331000 Test: Manually tested + unit tests Change-Id: I5dd81feaea5ff7dc0c7903612f0f1bc5c3cf22a2 (cherry picked from commit 9d6a3607f6ee3db03fe9fc2e686550078ca234f0)